The present disclosure generally relates to pollution control, and more particularly to reducing the dissolution of manganese present in a nanostructured material used for pollution control such as water treatment.
Natural or synthetic manganese-containing materials have been widely used in water treatment applications. Such materials are currently used to scavenge heavy metals from contaminated water such as drinking water and waste water. For example, manganese dioxide (MnO2) can oxidize metal ions such as ferrous ions in water. In some circumstances, the oxidized contaminants can undergo precipitation to allow them to be filtered from the water. Manganese dioxide can also be employed to adsorb lead in water. Manganese dioxide is particularly useful in removing arsenic from drinking water by oxidizing As(III) to As(V). The manganese dioxide has good As(V) adsorption capacity. Manganese (Mn3+) doped iron oxide is also an excellent adsorbent for As(V) in water. The use of hydrous manganese dioxide to remove radium from water has also been reported.
Unfortunately, the use of manganese-containing materials to remove contaminants from the water can result in the dissolution of manganese in the water such that it contains undesirable levels of manganese as defined by the National Sanitation Foundation International (NSFI, an independent, not-for-profit, non-governmental organization. In particular, the NSFI requires that materials in contact with drinking water shall not impart levels of extractable contaminants that exceed the maximum drinking water level (MDWL) value or the maximum contaminant concentration (MCC) value. The MDWL for manganese is 0.3 milligram/Liter (mg/L), and the MCC for manganese is 0.05 mg/L.